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CHARACTERIZING VORTICAL STRUCTURES IN THE LOWER LOG REGION OF THE ATMOSPHERIC BOUNDARY LAYER USING LARGE-SCALE PARTICLE TRACKING VELOCIMETRY

Giuseppe A. Rosi
Department of Mechanical Engineering, University of Calgary, Calgary, Canada; Department of Mechanical and Materials Engineering, Queen's University, Kingston, ON, Canada

Michael John Sherry
Fluids Laboratory for Aerospace and Industrial Engineering, Department of Mechanical and Aerospace Engineering, Monash University, Victoria, 3800, Australia; Department of Mechanical Engineering, University of Calgary, Calgary, Canada

Matthias Kinzel
Department of Fluid Mechanics and Aerodynamics (SLA), Technische Universitat Darmstadt Petersenstr. 30, 64287 Darmstadt, Germany; Graduate Aerospace Laboratories, California Institute of Technology, Pasadena, USA

David E. Rival
Department of Mechanical Engineering Massachusetts Institute of Technology 77 Massachusetts Avenue, Cambridge, MA 02139 USA; Department of Mechanical and Manufacturing Engineering University of Calgary 2500 University Dr NW, Calgary, AB, Canada T2N 1N4; Department of Mechanical and Materials Engineering, Queen’s University, Kingston, ON, Canada

Résumé

A large-scale particle tracking velocimetry (LS-PTV) system has been developed as a means of quantifying coherent structures within the atmospheric boundary layer. The LS-PTV system resolves three-dimensional, Lagrangian tracks over a volume of approximately 16m3. Mean velocity and Reynolds stresses have been validated and compared with wind-mast measurements and boundary-layer similarity formulations. The probability distributions for streamwise, spanwise and vertical velocity-fluctuation components agree with Gaussian distributions of equal variance. In contrast, the probability distributions for acceleration and vorticity are exponential and symmetric about zero. Thus, extreme acceleration events and vorticity events would be underpredicted by a Gaussian distribution. Finally, examples of particle paths exhibiting a high degree of swirl are presented, which are speculated to be signatures of large vortical structures.